1. Field of the Invention
The present invention relates to a vehicle generator mounted on a vehicle such as a passenger car or a truck.
2. Description of Related Art
There is known a vehicle-use power conversion apparatus having a structure in which a power conversion section is constituted of switching elements whose on/off timings are set in accordance with phase voltages of an armature winding of a vehicle generator. For example, refer to Japanese Patent No. 4275704. In this vehicle-use power conversion apparatus, the off timings and on timings of the switching elements are determined by comparing the phase voltages with a predetermined threshold voltage higher than the voltage of a vehicle battery.
However, the above conventional vehicle-use power conversion apparatus in which off timings of the switching elements are determined based on the phase voltages cannot start its rectifying operation until the phase voltages reach the predetermined threshold voltage. In some cases, this becomes a problem.
For example, when the switching elements are constituted of MOSFETs, it is possible to increase the output current of the vehicle generator by setting the off period of each switching element longer than a period in which a current flows through the body diode thereof in order to control the phase of the phase current so that a current flows from the vehicle battery into the phase winding through the switching element over a predetermined period (electrical angle). However, the above conventional vehicle-use power conversion apparatus cannot start such phase control while the rotational speed of the vehicle generator is so low that the phase voltage does not reach the threshold voltage, and accordingly the on/off control of the switching elements cannot be performed.